Wire arc additive manufacturing (WAAM) has emerged as a promising near-net-shape manufacturing technology for producing large-scale metallic components with high material utilization and cost-efficiency. However, the widespread adoption of aluminum alloys in WAAM remains challenging due to the complex interactions between process parameters, thermal history, microstructural evolution, defect formation, and mechanical performance. In this study, the influence of wire current on the microstructure, porosity evolution, crystallographic characteristics, residual strain distribution, and mechanical properties of CMT-WAAM-fabricated AA4043 deposits was systematically investigated. Quantitative porosity analysis using ImageJ revealed porosity area fractions of 0.138, 0.033, 0.257, and 2.704% for samples fabricated at 75, 100, 125, and  A, respectively, demonstrating the strong influence of heat input on pore formation. XRD confirmed the dominance of the α-Al phase across all processing conditions, while EBSD analysis revealed a transition from relatively refined cellular–dendritic structures at lower currents to coarse epitaxial columnar grains at higher heat inputs. Kernel average misorientation (KAM) analysis indicated progressive residual strain relaxation with increasing wire current due to enhanced thermal exposure. Excessive heat input at 150 A promoted abnormal grain growth (> 100 µm), significant porosity formation, and deterioration of mechanical properties. In contrast, the 125 A condition provided the most favorable balance of microstructural refinement, texture development (MUD = 11.55), low defect content, and residual strain distribution, resulting in the highest average microhardness (108 HV) and ultimate tensile strength (162 MPa). The findings establish a comprehensive process–structure–property relationship for CMT-WAAM-fabricated AA4043 and provide practical guidance for optimizing deposition parameters to minimize defects and enhance structural performance.